Vehicle traveling control device

ABSTRACT

A control device detects a first vehicle traveling in front of an own vehicle using a front looking radar device, and detects a second vehicle which is predicted to cut in between the own vehicle and the first vehicle using the front looking radar device and/or front-side looking radar devices. The control device calculates a first target acceleration required for the own vehicle to maintain an inter-vehicle distance between the own vehicle and the first vehicle at a first set inter-vehicle distance; and calculates a second target acceleration required for the own vehicle to maintain an inter-vehicle distance between the own vehicle and the second vehicle at a second set inter-vehicle distance. The control device selects either the first target acceleration or the second target acceleration and controls the own vehicle in such a manner that an actual acceleration of the own vehicle becomes closer to the mediated target acceleration.

The present application is an application for reissue of U.S. Pat. No.10,144,425, issued Dec. 4, 2018, which claims priority of JapaneseApplication No. 2015-186185, filed Sep. 23, 2015.

BACKGROUND

1. Field

The present disclosure relates to a vehicle travelling control devicewhich permits an own vehicle to follow an objective-forward-vehiclewhich is travelling/proceeding in front of (ahead of) the own vehicle soas to keep a predetermined inter-vehicle distance with respect to theobjective-forward-vehicle.

2. Description of the Related Art

A vehicle travelling control device that is conventionally known(hereinafter, referred to as a “conventional device”) predicts that theother vehicle will cut in between the own vehicle and theobjective-forward-vehicle, when the own vehicle is following (i.e.,trailing) the objective-forward-vehicle, and the lateral position of theother vehicle moves towards a travelling lane of the own vehicle with a(lateral) speed equal to or higher than a predetermined value.

In addition, the conventional device calculates a target accelerationbased on the other vehicle when the device predicts that the othervehicle will cut in, and controls an acceleration of the own vehicle inaccordance with the calculated acceleration (e.g., refer to JapaneseLaid Open Patent Application No. 2014-148293 (especially, paragraph0035, paragraph 0038, and FIG. 5).

SUMMARY

However, according to the conventional device, a problem may arise. Thatis, for example, the own vehicle may approach theobjective-forward-vehicle too quickly, when theobjective-forward-vehicle starts a rapid deceleration at a point in timeat which the conventional device predicts that the other vehicle willcut in, and the other vehicle does not actually cut in after theprediction.

The present disclosure addresses the problem described above. That is,one of the objects of the present disclosure is to disclose a vehicletravelling control device which can perform a more appropriate controlwhen it is predicted that the other vehicle will cut in between the ownvehicle and the objective-forward-vehicle.

The vehicle travelling control device according to the presentdisclosure (hereinafter, referred to as the “presently discloseddevice”) includes detecting means for detecting anobjective-forward-vehicle traveling in front of an own vehicle, and apredicted cut-in vehicle which is predicted to cut in between the ownvehicle and the objective-forward-vehicle (21, 22R, 22L, 20, step 310,step 420, step 440, step 810); first calculation means for calculating,as a target acceleration for trailing travel (G1tgt), a targetacceleration required for the own vehicle to maintain an inter-vehicledistance between the own vehicle and the objective-forward-vehicle at afirst set inter-vehicle distance (Dtgt) (20, step 320 to step 340);second calculation means for calculating, as a target acceleration for acut-in vehicle (G2tgt, G3tgt), a target acceleration required for theown vehicle to maintain an inter-vehicle distance between the ownvehicle and the predicted cut-in vehicle at a second set inter-vehicledistance (Dtgt) (20, step 430, step 435, step 455, step 460, step 820,step 830); mediation means for selecting, as a mediated targetacceleration (Gfin), either the target acceleration for the trailingtravel or the target acceleration for the cut-in vehicle, whichever issmaller (20, step 710, step 910); and travel control means forcontrolling a driving force and a brake force of the own vehicle in sucha manner that an actual acceleration of the own vehicle becomes closerto the mediated target acceleration (Gfin) (20, 30, 32, 40, 42, step720, step 920).

According to the present disclosure, the target acceleration requiredfor the own vehicle to maintain the inter-vehicle distance between theown vehicle and the objective-forward-vehicle at the first setinter-vehicle distance is calculated, as the target acceleration fortrailing travel. Also, the target acceleration required for the ownvehicle to maintain the inter-vehicle distance between the own vehicleand the predicted cut-in vehicle at the second set inter-vehicledistance is calculated, as the target acceleration for cut-in vehicle.Then, either the target acceleration for trailing travel or the targetacceleration for cut-in vehicle, whichever is smaller, is selected, asthe mediated target acceleration (Gfin). The acceleration of the ownvehicle is controlled in accordance with the mediated targetacceleration (Gfin). It should be noted that the first set inter-vehicledistance may be the same as or different from the second setinter-vehicle distance.

Generally, since the inter-vehicle distance between the own vehicle andthe predicted cut-in vehicle is shorter than the inter-vehicle distancebetween the own vehicle and the objective-forward-vehicle, the targetacceleration for cut-in vehicle is smaller than the target accelerationfor trailing travel. Accordingly, when the predicted cut-in vehicle isdetected, the target acceleration for cut-in vehicle is selected as themediated target acceleration frequently, according to the presentlydisclosed device. Thus, the own vehicle decelerates so as to increasethe inter-vehicle distance between the own vehicle and theobjective-forward-vehicle. Consequently, when the predicted cut-invehicle actually cuts in, the inter-vehicle distance between the ownvehicle and the predicted cut-in vehicle becomes appropriate in a shorttime.

On the other hand, if the objective-forward-vehicle starts to rapidlydecelerate after a point in time at which the predicted cut-in vehicleis detected, the target acceleration for trailing travel becomes smallerthan the target acceleration for cut-in vehicle. Therefore, in thiscase, the target acceleration for trailing travel is selected as themediated target acceleration, according to the presently discloseddevice. Accordingly, the own vehicle decelerates so as to ensure/acquirean appropriate inter-vehicle distance between the own vehicle VA and theobjective-forward-vehicle. As a result, the inter-vehicle distancebetween the own vehicle and the objective-forward-vehicle becomingexcessively short can be avoided when the predicted cut-in vehicle doesnot actually cut in.

In one of aspects of the presently disclosed device, the detecting meansincludes a front looking radar device (21), whose detection area has acenter axis extending in a straight forward direction (C1) of the ownvehicle, which detects the target object to obtain first target objectinformation concerning the target object; a front-side looking radardevice (22R, 22L), whose detection area has a center axis extending in adiagonally forward direction (CL or CR) of the own vehicle, whichdetects the target object to obtain second target object informationconcerning the target object; and predicted cut-in vehicle detectingmeans for integrating the first target object information and the secondtarget object information to obtain an integrated target objectinformation, and detecting the predicted cut-in vehicle based on theintegrated target object information, when the front looking radardevice and the front-side looking radar device detect an identicaltarget object (20, step 410, step 415, step 420), and for detecting thepredicted cut-in vehicle based on the second target object informationbut not based on the first target object information, when thefront-side looking radar device detects an target object, but the frontlooking radar device does not detect the target object (20, step 410,step 440).

Further, the second calculation means is configured to calculate thetarget acceleration for cut-in vehicle in such a manner that the targetacceleration for cut-in vehicle is allowed to be a negative accelerationachieved when a brake device of the own vehicle is operated, in a casewhere the predicted cut-in vehicle is detected based on the integratedtarget object information (20, step 435), and calculate the targetacceleration for cut-in vehicle while providing a limitation on thetarget acceleration for cut-in vehicle in such a manner that the targetacceleration for cut-in vehicle does not become smaller than a negativeacceleration achieved when a throttle valve opening of an internalcombustion engine serving as a driving force of the own vehicle is setat a minimum value while the brake device of the own vehicle is notoperated, in a case where the predicted cut-in vehicle is detected basedon the second target object information but not based on the firsttarget object information (20, step 460).

The detection area of the front looking radar device and the detectionarea of the front-side looking radar device have a portion that overlapswith each other (refer to FIG. 1 ). Further, the front looking radardevice is a main radar for obtaining information necessary for thetrailing travel. Therefore, generally, an accuracy of the informationobtained by the front looking radar (e.g., a relative distance for thetarget object) is higher than an accuracy of the information obtained bythe front-side looking radar.

Thus, the predicted cut-in vehicle detecting means in the above aspectintegrates the target object information obtained by the front lookingradar device (first target object information) and the target objectinformation obtained by the front-side looking radar device (secondtarget object information) to obtain the integrated target objectinformation, when the front looking radar device and the front-sidelooking radar device detect the identical target object. Further, thesecond calculation means calculates the target acceleration for cut-invehicle based on the integrated target object information. In this case,the integrated target object information is based on the first targetobject information obtained by the front looking radar device havingrelatively higher accuracy, and thus, the detecting accuracy for thepredicted cut-in vehicle is higher than the detecting accuracy for thepredicted cut-in vehicle which is detected based solely on thefront-side looking radar device having relatively lower accuracy.Therefore, the possibility that the predicted cut-in vehicle does notactually cut in is relatively low. In view of the above, the secondcalculation means calculates the target acceleration for cut-in vehiclein such a manner that the target acceleration for cut-in vehicle isallowed to be the “negative acceleration whose absolute value is large(that is, large deceleration)” achieved when the brake device of the ownvehicle is operated.

In contrast, when the predicted cut-in vehicle is detected based solelyon the “second target object information obtained by the front-sidelooking radar device”, the detecting accuracy for the predicted cut-invehicle is relatively low. Thus, the possibility that the predictedcut-in vehicle does not actually cut in is relatively high. Therefore,if the target acceleration for cut-in vehicle is allowed to become the“negative acceleration whose absolute value is large” achieved when thebrake device of the own vehicle is operated, a relatively rapiddeceleration frequently occurs when the actual cut-in does not occur.This may provide an odd feeling to the driver.

In view of the above, when the predicted cut-in vehicle is detectedbased solely on the information obtained by the front-side looking radardevice, the second calculation means calculates the target accelerationfor cut-in vehicle while providing a limitation on the targetacceleration for cut-in vehicle in such a manner that the targetacceleration for cut-in vehicle does not become smaller than a negativeacceleration achieved when a throttle valve opening of an internalcombustion engine serving as a driving force of the own vehicle is setat a minimum value. As a result, the own vehicle does not rapidlydecelerate due to the predicted cut-in vehicle. Thus, even when theactual cut-in does not actually occur, the driver avoids the odd feelingof rapid deceleration.

In the above description, references used in the following descriptionsregarding embodiments are added with parentheses to the elements of thepresent disclosure, in order to assist in understanding the presentdisclosure. However, those references should not be used to limit thescope of the invention. Other objects, other features, and accompanyingadvantages of the present disclosure will be readily understood from thedescription of embodiments of the present disclosure to be givenreferring to the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a vehicle travelling control deviceaccording to a first embodiment of the present disclosure.

FIG. 2 is a configuration diagram of the vehicle travelling controldevice shown in FIG. 1 .

FIG. 3 is a flowchart showing a routine executed by a CPU of the drivingsupport ECU shown in FIG. 2 .

FIG. 4 is a flowchart showing a routine executed by the CPU of thedriving support ECU shown in FIG. 2 .

FIG. 5 is a look-up table (map) which the CPU of the driving support ECUshown in FIG. 2 refers to in order to detect a predicted cut-in vehicle.

FIG. 6 (A) is a view schematically showing a scene when the othervehicle changes lanes, and FIG. 6 (B) is a view schematically showinganother scene when the other vehicle changes lanes.

FIG. 7 is a flowchart showing a routine executed by the CPU of thedriving support ECU shown in FIG. 2 .

FIG. 8 is a flowchart showing a routine executed by a CPU of a vehicletravelling control device according to a second embodiment of thepresent disclosure.

FIG. 9 is a flowchart showing a routine executed by the CPU of thevehicle travelling control device according to the second embodiment ofthe present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Each of vehicle travelling control devices according to the presentdisclosure will next be described with reference to the drawings.Firstly, main terms used in the present specification and the drawingsare described.

-   -   The own vehicle: One's own vehicle (subject vehicle that is        focused on).    -   The other vehicle: A vehicle other than the own vehicle.    -   The proceeding vehicle: The other vehicle traveling immediately        ahead of (in front of) the own vehicle.    -   The objective-forward-vehicle: The proceeding/leading vehicle,        which a sensor device (front looking radar device) mounted on        the own vehicle detects (acquires), and which the own vehicle        should follow up by controlling an acceleration of the own        vehicle so as to keep an inter-vehicle distance between the own        vehicle and the proceeding vehicle at a predetermined distance.    -   The cut-in vehicle: The other vehicle which cuts in ahead of the        own vehicle by changing lanes.

First Embodiment Structure

As shown in FIG. 1 , a vehicle travelling control device (hereinafter,sometimes referred to as a “first device”) 10 according to a firstembodiment of the present disclosure is mounted on (applied to) the ownvehicle VA. The first vehicle 10 comprises a driving support (assist)ECU 20, an engine ECU 30, and a brake ECU 40. Those ECUs are capable ofexchanging data (communicating with each other) through acommunication/sensor CAN (Controller Area Network) 100. It should benoted that an “ECU” is an abbreviation of an electric control unit, andis an electronic control circuit having a microcomputer including a CPU,a ROM, a RAM, an interface, and the like, as a main part. The CPUachieves/realizes various functions described later by executinginstructions (routines) stored in the memory (e.g., ROM).

Further, the first device 10 comprises a front looking radar device 21,a front-side looking radar device 22R, and a front-side looking radardevice 22L. Those radar devices can also exchange data with the drivingsupport ECU 20 through the CAN 100.

More specifically, as shown in FIG. 2 , the driving support ECU 20 isconnected with an ACC operation switch 23, and a vehicle speed sensor24, in addition to the front looking radar device 21, the front-sidelooking radar device 22R, and the front-side looking radar device 22L.

The front looking radar device 21 comprises a millimeter wavetransmitter-receiver section, and a processing section. As shown in FIG.1 , the front looking radar device 21 is positioned at the front end ofthe own vehicle VA, and at the center portion of the own vehicle VA in abody width direction. The millimeter wave transmitter-receiver sectiontransmits a millimeter wave which propagates with a center axis C1extending in a straight forward direction of the own vehicle VA, andspreads with a predetermined angle θ1 in a left direction as well aswith the predetermined angle θ1 in a right direction with respect to thecenter axis C1. The millimeter wave is reflected by a target object(e.g., proceeding vehicle). The millimeter wave transmitter-receiversection receives the reflected wave. It should be noted that,hereinafter, a vehicle going forward direction along the center axis C1is defined as an “X-axis”, and a direction orthogonal to the center axisC1 is defined as a “Y-axis.” The X-coordinate is positive in thevehicle's forward direction, and is negative in the vehicle's backwarddirection. The Y-coordinate is positive in the vehicle's rightwarddirection, and is negative in the vehicle's leftward direction.

The processing section of the front looking radar device 21 obtains,every elapse of a predetermined time, an inter-vehicle distance(longitudinal distance) Dfx(n), a relative speed Vfx(n), a lateraldistance Dfy(n), a relative lateral speed Vfy(n), or the like, withrespect to each detected target object (n), based on a phase differencebetween the transmitted millimeter wave and the received reflected wave,an attenuation level, a time period from the point in time at which themillimeter wave is transmitted to the point in time at which thereflected wave is received, or the like. The data (Dfx(n), Vfx(n),Dfy(n), Vfy(n), etc.) acquired by the front looking radar device 21 arealso referred to as “front looking radar obtained information”, as amatter of convenience.

The inter-vehicle distance (longitudinal distance) Dfx(n) is a distancealong the center axis C1 between the own vehicle VA and the targetobject(n) (e.g., the proceeding vehicle).

The relative speed Vfx(n) is a difference (=SPDs−SPDj) between a speedSPDs of the target object(n) (e.g., the proceeding vehicle) and a speedSPDj of the own vehicle VA. It should be noted that the speed SPDs ofthe target object(n) is a speed of the target object (n) in thedirection of travel of the own vehicle VA.

The lateral distance Dfy(n) is a distance along the direction orthogonalto the center axis C1 from the center axis C1 to a “center position ofthe target object (n) (e.g., a center position of a vehicle width of theproceeding vehicle).” The lateral distance Dfy(n) may also be referredto as a “lateral position.”

The relative lateral speed Vfy(n) is a speed of the center position ofthe each target object (n) in the direction orthogonal to the centeraxis C1.

As shown in FIG. 1 , the front-side (left) looking radar device 22L ispositioned at a left-and-front side of the vehicle body of the ownvehicle VA. The front-side looking radar device 22L has a configurationsimilar to the configuration of the front looking radar device 21. Themillimeter wave transmitter-receiver section of the front-side lookingradar device 22L transmits a millimeter wave which propagates with acenter axis CL extending in a front-left direction of the own vehicleVA, and spreads with a predetermined angle θ2 in a front direction aswell as the predetermined angle θ2 in a rear direction with respect tothe center axis CL. One of the border lines (CLx) defining the border ofthe spreading millimeter wave transmitted from the front-side lookingradar device 22L is parallel with the center axis C1.

The processing section of the front-side looking radar device 22Lobtains, every elapse of a predetermined time, a longitudinal distanceDLx, a relative speed VLx, a lateral distance DLy, a relative lateralspeed VLy, or the like, with respect to each detected target object,based on a phase difference between the transmitted millimeter wave andthe received reflected wave, an attenuation level, a time period fromthe point in time at which the millimeter wave is transmitted to thepoint in time at which the reflected wave is received, or the like. Avertical axis of coordinates of those data is the center axis CL, and ahorizontal axis of the coordinates of those data is an axis extending ina direction orthogonal to the center axis CL. Those data (DLx, VLx, DLy,VLy, or the like) obtained by the front-side looking radar device 22Lare also referred to as “front-left-side looking radar obtainedinformation”, as a matter of convenience. It should be noted that anaccuracy of the front-left-side looking radar obtained information islower than an accuracy of the front looking radar obtained information.

As shown in FIG. 1 , the front-side (right) looking radar device 22R ispositioned at a right-and-front side of the vehicle body of the ownvehicle VA. The front-side looking radar device 22R has a configurationsimilar to the configuration of the front looking radar device 21 andthe front-side looking radar device 22L. The millimeter wavetransmitter-receiver section of the front-side looking radar device 22Rtransmits a millimeter wave which propagates with a center axis CRextending in a front-right direction of the own vehicle VA, and spreadswith a predetermined angle θ2 in a front direction as well as thepredetermined angle θ2 in a rear direction with respect to the centeraxis CL. One of the border lines (CRx) defining the border of thespreading millimeter wave transmitted from the front-side looking radardevice 22R is parallel with the center axis C1.

The processing section of the front-side looking radar device 22Robtains, every elapse of a predetermined time, a longitudinal distanceDRx, a relative speed VRx, a lateral distance DRy, a relative lateralspeed VRy, or the like, with respect to each detected target object,based on a phase difference between the transmitted millimeter wave andthe received reflected wave, an attenuation level, a time period fromthe point in time at which the millimeter wave is transmitted to thepoint in time at which the reflected wave is received, or the like. Avertical axis of coordinates of those data is the center axis CR, and ahorizontal axis of the coordinates of those data is an axis extending ina direction orthogonal to the center axis CR. Those data (DRx, VRx, DRy,VRy, or the like) obtained by the front-side looking radar device 22Rare also referred to as “front-right-side looking radar obtainedinformation”, as a matter of convenience. It should be noted that anaccuracy of the front-right-side looking radar obtained information isthe same as the accuracy of the front-left-side looking radar obtainedinformation, and is lower than the accuracy of the front looking radarobtained information.

As is clear from FIG. 1 , the detection area of the front looking radardevice 21 and the detection area of the front-side looking radar device22L have a portion (overlap area AL) that overlaps with each other, andthe detection area of the front looking radar device 21 and thedetection area of the front-side looking radar device 22R have a portion(overlap area AR) that overlaps with each other. In other words, atarget object within the overlap area AL is detected/captured by both ofthe front looking radar device 21 and the front-side looking radardevice 22L, and a target object within the overlap area AR isdetected/captured by both of the front looking radar device 21 and thefront-side looking radar device 22R.

Referring back to FIG. 2 again, the ACC operation switch 23 is a switchoperated by a driver. The term “ACC” means an inter-vehicle distancecontrol (Adaptive Cruise Control), and may also be simply referred to asa “trailing travel control.” When the driver performs a certainoperation using the ACC operation switch 23, an ACC start request(including an ACC resume request) and an ACC termination request (cancelrequest) are generated according to the operation. Further, according toa certain operation using the ACC operation switch 23, a targetinter-vehicle time Ttgt described later is set or changed.

The vehicle speed sensor 24 detects a speed (own vehicle speed) Vj ofthe own vehicle VA, and generates a signal indicative of the own vehiclespeed Vj.

The engine ECU 30 is connected with a plurality of engine sensors 31 toreceive detected signals from those sensors. The engine sensors 31 aresensors that detect various operation state parameters of anunillustrated own vehicle's “gasoline fuel injection type/sparkignition/internal combustion engine.” The engine sensors 31 include anacceleration pedal operation amount sensor, a throttle valve openingsensor, an engine rotational speed sensor, an intake air-flow sensor, orthe like.

Further, the engine ECU is connected with engine actuators 32 includinga throttle valve actuator, fuel injectors, or the like. The engine ECU30 drives the engine actuators 32 to change a torque generated by theinternal combustion engine, and thereby, adjusting a driving force ofthe own vehicle so as to control an acceleration of the own vehicle VA.In addition, the engine ECU 30 performs a “fuel-cut operation” to stop afuel injection, when the throttle valve opening degree detected by thethrottle valve opening sensor is “0 (or the minimum value within a rangethat the throttle valve opening can become)” (namely, the throttle valveis fully-closed) and the engine rotational speed is higher than anengine rotational speed threshold.

The brake ECU 40 is connected with a plurality of brake sensors 41 toreceive detected signals from those sensors. The brake sensors 41 aresensors that detect various parameters used for controlling anunillustrated “brake device (hydraulic type friction brake device) ofthe own vehicle VA.” The brake sensors 41 include a brake pedaloperation amount sensor, a wheel rotational speed sensor detecting arotational speed of each wheel, or the like.

Further, the brake ECU 40 is connected with brake actuators 42. Thebrake actuators 42 are actuators for controlling pressure of brake oil.The brake actuators 42 are positioned in an unillustrated hydrauliccircuit between an unillustrated master cylinder for pressurizing thebrake oil according to a brake pedal force and unillustrated frictionbrake devices including well-known wheel cylinders provided to wheels.The brake actuators 42 adjust the pressure of the brake oil supplied tothe wheel cylinders. The brake ECU 40 drives the brake actuators 42 togenerate a brake force (friction brake force) at each of the wheels, tothereby control/adjust the acceleration (negative acceleration, that is,deceleration) of the own vehicle VA.

(Outline of Operation)

The first device specifies a objective-forward-vehicle based on thetarget object information obtained by the front looking radar device 21,and calculates a target acceleration G1tgt for trailing travel, requiredto keep a first set inter-vehicle distance with respect to theobjective-forward-vehicle.

Further, when the front looking radar device 21 and the front-sidelooking radar device 22L or 22R detect the same (identical) targetobject, the first device integrates/merges the target object informationdetected by the front looking radar device 21 and the target objectinformation detected by the front-side looking radar device 22L or 22R,and determines whether or not there is a predicted cut-in vehicle basedon the integrated/merged target object information. Thereafter, when thefirst device determines that there is the predicted cut-in vehicle, itcalculates a target acceleration G2tgt for cut-in vehicle, required tokeep a second set inter-vehicle distance with respect to that predictedcut-in vehicle.

Furthermore, when one of the front-side looking radar device 22L and thefront-side looking radar device 22R detects the target object, but thefront looking radar device 21 does not detect that target object, thefirst device determines whether or not there is a predicted cut-invehicle based on the target object information detected by one of thefront-side looking radar device 22L and the front-side looking radardevice 22R. Thereafter, when the first device determines that there isthe predicted cut-in vehicle, it calculates a target acceleration G3tgtfor cut-in vehicle, required to keep a third set inter-vehicle distancewith respect to that predicted cut-in vehicle.

In addition, the first device selects a minimum (the smallest) targetacceleration among the target acceleration G1tgt for trailing travel,the target acceleration G2tgt for cut-in vehicle, and the targetacceleration G3tgt for cut-in vehicle (i.e., selects one of G1tgt,G2tgt, and G3tgt, whichever smallest), and sets the selected targetacceleration, as a “final target acceleration (mediated/adjusted targetacceleration) Gfin.” Thereafter, the first device controls (drives) theengine actuators 32 and the brake actuators 42 in such a manner that theactual acceleration of the own vehicle VA becomes equal to the mediatedtarget acceleration Gfin. As a result, the actual acceleration of theown vehicle VA is made to become equal to the mediated targetacceleration Gfin.

(Specific Operation)

The CPU of the driving support ECU 20 (hereinafter, a “CPU”indicates/means the CPU of the driving support ECU 20, unless otherwisenoted) executes routines shown in the flowcharts illustrated in FIGS.4-7 , every elapse of a predetermined time, when the ACC start requestis generated by the operation using the ACC operation switch 23while/when the trailing inter-vehicle distance control is not beingperformed.

1. Calculation of the Target Acceleration for Trailing Travel

Therefore, at an appropriate point in time, the CPU starts processingfrom step 300 shown in FIG. 3 to execute processes from step 310 to step340 described below in this order, and then, proceeds to step 395 so asto end the present routine tentatively. The routine shown in FIG. 3 is aroutine for calculating the target acceleration for trailing travel.

Step 310: The CPU selects/specifies the objective-forward-vehicle basedon the front looking radar obtained information. More specifically, theCPU applies the lateral distance Dfy(n) and the inter-vehicle distanceDfx(n) to a map (look-up table) shown in a block of step 310 so as toselect/specify, as the objective-forward-vehicle (a), the other vehicle(n) existing in an objective-forward-vehicle area defined by the map. Itshould be noted that, if there are a plurality of the other vehicles inthe objective-forward-vehicle area, the CPU specifies one of the othervehicles, that has the shortest inter-vehicle distance Dfx(n), as theobjective-forward-vehicle. Further, if there is noobjective-forward-vehicle, the CPU controls the acceleration of the ownvehicle VA in such a manner that the speed of the own vehicle VA becomesequal to a target speed depending on (according to) the targetinter-vehicle time Ttgt. This point does not directly relate to thepresent disclosure, and thus, is not described in detail.

Step 320; The CPU calculates the target inter-vehicle distance Dtgt bymultiplying the target inter-vehicle time Ttgt by the speed Vj of theown vehicle. The target inter-vehicle time Ttgt is separately set basedon the operation of the ACC operation switch 23, however, it may beconstant. It should be noted that the target inter-vehicle distance Dtgtobtained at step 320 is also referred to as a “first set inter-vehicledistance.”

Step 330; The CPU calculates an inter-vehicle deviation (difference) ΔD1by subtracting the target inter-vehicle distance Dtgt from theinter-vehicle distance Dfx(a) of the objective-forward-vehicle (a)selected/specified at step 310.

Step 340; The CPU calculates the target acceleration G1tgt for trailingtravel using either one of a formula (1) described below and a formula(2) described below. The target acceleration G1tgt for trailing travelis also referred to as a “first target acceleration”, as a matter ofconvenience.

In the formulas (1) and (2), the Vfx(a) is the relative speed of theobjective-forward-vehicle (a) selected/specified at step 310, and K1 andK2 are predetermined positive gains (coefficients). The CPU uses theformula (1) below when a value (K1·ΔD1+K2·Vfx(a)) is positive. Ka1 is apositive gain (coefficient) for acceleration, and set to a value equalto or smaller than “1.”. The CPU uses the formula (2) below when a value(K1·ΔD1+K2·Vfx(a)) is negative. Kd1 is a gain (coefficient) fordeceleration, and set to “1” in the present example.G1tgt(for acceleration)=Ka1·(K1·ΔD1+K2·Vfx(a))  (1)G1tgt(for deceleration)=Kd1·(K1·ΔD1+K2·Vfx(a))  (2)

The target acceleration G1tgt for deceleration calculated based on theformula (2) above is calculated in such a manner that the targetacceleration G1tgt is allowed to be an acceleration (negativeacceleration) realized/achieved when the brake device of the own vehicleVA is operated (in other words, the target acceleration G1tgt may be avalue obtained under a condition that it is allowed to be a negativeacceleration realized/achieved when the brake device is operated). Inthe above manner, the target acceleration G1tgt for trailing travelbased solely/only on the front looking radar obtained information isacquired.

2. Calculation of the Target Acceleration for Cut-in Vehicle

Further, at an appropriate point in time, the CPU starts processing fromstep 400 in a “routine for calculation of the target acceleration forcut-in vehicle” shown in FIG. 4 to proceed to step 405. At step 405, theCPU transforms coordinates concerning the position of the target objectand the relative speed, obtained by the front-side looking radar device22L and the front-side looking radar device 22R (that is, thefront-left-side looking radar obtained information, and thefront-right-side looking radar obtained information) to the “X-Ycoordinates of the front looking radar device 21.” Consequently, the“coordinate transformed front-side looking radar information FSXn”,including an inter-vehicle distance Dsx, a relative speed Vsx, a lateraldistance Dsy, and a relative lateral speed Vsy, is obtained.

Subsequently, the CPU proceeds to step 410 to compare the front lookingradar obtained information FRXn with/to the coordinate transformedfront-side looking radar information FSXn in order to determine whetheror not there is a “target object which at least one of the front-sidelooking radar device 22L and the front-side looking radar device 22Rdetects” among the target objects which the front looking radar device21 detects and which are different from (other than) theobjective-forward-vehicle (a).

When the determination at step 410 is positive (affirmative), the CPUproceeds to step 415 at which the CPU integrates/merges the targetobject information according to a formula (3) described below. That is,at step 415, the CPU obtains integrated target object information. α(t)in the formula (3) described below is a filtering coefficient (weightingcoefficient), and is obtained by applying a time t to a look up tableMapα(t) shown in a block B1 in FIG. 4 . The time t is an elapsed timefrom a point in time at which the front looking radar device 21 startsto detect the “target object” which either one of the front-side lookingradar device 22L and the front-side looking radar device 22R has beendetecting. According to the table Mapα(t), α(t) is obtained as a valuewhich gradually becomes closer to “1” from a value α0 between “0” and“1” as the elapsed time t becomes longer. It should be noted that α(t)may be a constant value between “0” and “1”, which does not changedepending upon the elapsed time t.Integrated value=α(t)·FRXn+(1−α(t))·FSXn  (3)

The front looking radar obtained information FRXn in the formula (3)above includes “an inter-vehicle distance Dfx (b), a relative speedVfx(b), a lateral distance Dfy(b), and a relative lateral speed Vfy(b)”concerning the “target object (hereinafter, referred to as a “commontarget object (b)”) which was determined at step 410 to be detected bynot only the front looking radar device 21 but also either one of thefront-side looking radar device 22L and the front-side looking radardevice 22R. The coordinate transformed front-side looking radarinformation FSXn in the formula (3) above includes “a coordinatetransformed inter-vehicle distance Dsx, a coordinate transformedrelative speed Vsx, a coordinate transformed lateral distance Dsy, and acoordinate transformed relative lateral speed Vsy” concerning the commontarget object (b). Accordingly, as shown in formulas from (4) to (7)described below, “an integrated inter-vehicle distance Dmx, anintegrated relative speed Vmx, an integrated lateral distance Dmy, andan integrated relative lateral speed Vmy” serving as the integratedvalues are obtained.Dmx=α(t)·Dfx(b)+(1−α(t))−Dsx  (4)Vmx=α(t)·Vfx(b)+(1−α(t))·Vsx  (5)Dmy=α(t)·Dfy(b)+(1−α(t))·Dsy  (6)Vmy=α(t)−Vfy(b)+(1−α(t))·Vsy   (7)

Subsequently, the CPU proceeds to step 420 to determine whether or notthe there is a predicted cut-in vehicle (i.e., whether or not a vehiclewhich is predicted to cut in exists). More specifically, the CPU obtainsa cut-in event probability P by applying “the integrated lateraldistance Dmy and the integrated relative speed Vmy” to an area map WSshown in FIG. 5 .

For example, when a vehicle traveling in front and diagonally to theleft of the own vehicle VA cuts in between the own vehicle VA and theobjective-forward-vehicle (a), a trajectory (locus) of a point definedby the integrated lateral distance Dmy and the integrated relativelateral speed Vmy changes as shown by a broken line TL in FIG. 5 . Thearea map WS is made in consideration of such trajectories, and is storedin the ROM beforehand. Generally speaking, the cut-in event probabilityP obtained using the area map WS becomes higher as an magnitude of theintegrated lateral distance Dmy becomes closer to “0”, and becomeshigher as a magnitude |Vmy| of the integrated relative lateral speed Vmybecomes larger when the integrated relative lateral speed Vmy is a valueindicating that the vehicle is approaching the center portion of thewidth of the own vehicle.

The CPU determines that there is the “predicted cut-in vehicle”, whenthe CPU determines that the cut-in event probability P obtained usingthe area map WS is equal to or higher than a predetermined value (e.g.,60%). That is, the CPU specifies that target object as the predictedcut-in vehicle.

When it is determined that there is the predicted cut-in vehicle, theCPU makes a “Yes” determination at step 420 to execute processes of step430 and step 435 described below in this order, and then, proceeds tostep 495 so as to end the present routine tentatively.

Step 430: The CPU calculates an inter-vehicle deviation (difference) ΔD2by subtracting the target inter-vehicle distance Dtgt from theintegrated inter-vehicle distance Dmx. It should be noted that thetarget inter-vehicle distance Dtgt used at step 430 is referred to as a“second set inter-vehicle distance”, as a matter of convenience. Thesecond set inter-vehicle distance may be the same as the first setinter-vehicle distance, or may be a value which becomes closer to thefirst set inter-vehicle distance from a value smaller than the first setinter-vehicle distance by a positive first value as an “elapsed time tfrom a point in time at which it was determined that there was thepredicted cut-in vehicle” becomes longer. In this case, the targetinter-vehicle time for calculating the second set inter-vehicle distancemay be a time obtained by multiplying the “target inter-vehicle timeTtgt used when the first set inter-vehicle distance is calculated” by a“coefficient s(t)” which comes closer to and converges on “1” from avalue between “0” and “1” as the above mentioned time t becomes longer.

Step 435: The CPU calculates the target acceleration G2tgt for cut-invehicle according to either one of a formula (8) and a formula (9)described below. The target acceleration G2tgt for cut-in vehicle isreferred to as a “second target acceleration”, as a matter ofconvenience. Further, the CPU sets a target acceleration G3tgt forcut-in vehicle described later at an “imaginary acceleration G3infinite”which is larger than a maximum acceleration that the own vehicle VA canrealize.

In the formula (8) and the formula (9), Vmx is the integrated relativespeed of the target object which was determined to be the predictedcut-in vehicle at step 420, and “K1, and K2” are the same gains as the“K1, and K2” used in the formula (1) and the formula (2), respectively.The CPU uses the formula (8) below when a value (K1·ΔD2+K2·Vmx) ispositive.

Ka2 is a positive gain (coefficient) for acceleration, and set at avalue smaller than the gain Ka1 used in the formula (1) above.

The CPU uses the formula (9) below when the value (K1·ΔD2+K2·Vmx) isnegative.

Kd2 is a positive gain (coefficient) for deceleration, and set at avalue smaller than the gain Kd1 used in the formula (2) above.G2tgt(for acceleration)=Ka2·(K1·ΔD2+K2·Vmx)  (8)G2tgt(for deceleration)=Kd2·(K1·ΔD2+K2·Vmx)  (9)

The target acceleration G2tgt for cut-in vehicle for decelerationcalculated based on the formula (9) above is calculated in such a mannerthat the target acceleration G2tgt is allowed to be an acceleration(negative acceleration) realized/achieved when the brake device of theown vehicle VA is operated, similarly to the target acceleration G1tgtfor trailing travel. In other words, the target acceleration G2tgt forcut-in vehicle may become a value obtained under the condition that itis allowed to be a negative acceleration realized/achieved when thebrake device is operated. In the above manner, the target accelerationG2tgt for cut-in vehicle is calculated based on the integrated/mergedinformation (integrated values) obtained by integrating the frontlooking radar obtained information and the coordinate transformedfront-side looking radar information.

In contrast, when the CPU determines that there is no predicted cut-invehicle upon the execution of step 420, the CPU makes a “No”determination at step 420 to proceed to step 425, at which the CPU setsthe target acceleration G2tgt for cut-in vehicle at an “imaginaryacceleration G2infinite” which is larger than the maximum accelerationthat the own vehicle VA can realize, and sets the target accelerationG3tgt for cut-in vehicle described later at the “imaginary accelerationG3infinite” which is larger than the maximum acceleration that the ownvehicle VA can realize. Thereafter, the CPU proceeds to step 495 to endthe present routine tentatively.

On the other hand, when the determination at step 410 is negative(unaffirmative), the CPU makes a “No” determination. Then, the CPUproceeds to step 440, at which the CPU determines whether or not thereis a predicted cut-in vehicle. In this case, the CPU obtains the cut-inevent probability P by applying “the coordinate transformed lateraldistance Dsy in place of the integrated lateral distance Dmy, and thecoordinate transformed relative lateral speed Vsy in place of theintegrated relative speed Vmy” to the area map WS shown in FIG. 5 .Thereafter, the CPU determines that there is the “predicted cut-invehicle”, when the cut-in event probability P is equal to or larger thanthe predetermined value (e.g., 60%), similarly to step 420. That is, theCPU specifies that target object as the predicted cut-in vehicle.

When it is determined that there is the predicted cut-in vehicle, theCPU makes a “Yes” determination at step 440 to proceed to step 450, atwhich the CPU determines whether or not a lane change (changing lanes)of the predicted cut-in vehicle occurs in front of the own vehicle VA.

For example, as shown in (A) of FIG. 6 , when the vehicle VC is cuttingin while the own vehicle VA is following the objective-forward-vehicleVB, it is determined that the vehicle VC is the predicted cut-invehicle. In this case, if the speed Vj of the own vehicle VA is 80 km/h,and the speed of the predicted cut-in vehicle VC is 85 km/h, it islikely that the predicted cut-in vehicle VC will cut in between the ownvehicle VA and the objective-forward-vehicle VB.

In contrast, as shown in (B) of FIG. 6 , when the own vehicle VA isfollowing (i.e., trailing) the objective-forward-vehicle VB at 80 km/h,and the speed of the predicted cut-in vehicle VC is 60 km/h, it islikely that the predicted cut-in vehicle VC will change lanes to travelbehind the own vehicle VA, after the own vehicle VA passes the predictedcut-in vehicle VC.

Step 450 is for determining which situation is occurring, the situationshown in (A) of FIG. 6 , or the situation shown in (B) of FIG. 6 . Morespecifically, the CPU determines whether or not the coordinatetransformed relative speed Vsx is equal to or higher than apredetermined threshold Vth so as to determine whether or not thechanging lanes of the predicted cut-in vehicle occurs in front of theown vehicle VA. It should be noted the predetermined threshold Vth maybe set at a value larger than a negative certain value.

When it is determined that the changing lanes of the predicted cut-invehicle occurs in front of the own vehicle VA (i.e., when it isdetermined that the coordinate transformed relative speed Vsx is equalto or higher than the predetermined threshold Vth), the CPU makes a“Yes” determination at step 450 to execute processes of step 455 andstep 460 described below in this order, and then, proceeds to step 495so as to end the present routine tentatively.

Step 455: The CPU calculates an inter-vehicle deviation (difference) ΔD3by subtracting the target inter-vehicle distance Dtgt from thecoordinate transformed inter-vehicle distance Dsx. It should be notedthat the target inter-vehicle distance Dtgt used at step 455 is referredto as a “third set inter-vehicle distance”, as a matter of convenience.The third set inter-vehicle distance may be the same as the second setinter-vehicle distance, or may be a value which becomes closer to thefirst set inter-vehicle distance from a value smaller than the secondset inter-vehicle distance by a positive first value as the “elapsedtime t from the point in time at which it was determined that there wasthe predicted cut-in vehicle” becomes longer. In this case, the targetinter-vehicle time for calculating the third set inter-vehicle distancemay be a time obtained by multiplying the “target inter-vehicle timeTtgt used when the first set inter-vehicle distance is calculated” by a“coefficient u(t)” which comes closer to and converges on “1” from avalue between “0” and “1” and smaller than the coefficient s(t)=s(0) asthe above mentioned time t becomes longer. It should be noted that thecoefficient u(t) is adjusted so as to be equal to or smaller than thecoefficient s(t).

Step 460: The CPU calculates the target acceleration G3tgt for cut-invehicle according to either one of a formula (10) and a formula (11)described below. The target acceleration G3tgt for cut-in vehicle isreferred to as a “third target acceleration”, as a matter ofconvenience. Further, the o CPU sets the target acceleration G2tgt forcut-in vehicle at the “imaginary acceleration G2infinite” which islarger than the maximum acceleration that the own vehicle VA canrealize.

In the formula (10) and the formula (11), Vsx is the coordinatetransformed relative speed of the target object which was determined tobe the predicted cut-in vehicle at step 440, and “K1, and K2” are thesame gains as the “K1, and K2” used in the formula (1) and the formula(2), respectively. The CPU uses the formula (10) below when a value(K1·ΔD3+K2·Vsx) is positive.

Ka3 is a positive gain (coefficient) for acceleration, and set at avalue smaller than (or equal to) the gain Ka2 used in the formula (8)above.

The CPU uses the formula (1) below when the value (K1·ΔD3+K2·Vsx) isnegative.

Kd3 is a positive gain (coefficient) for deceleration, and set at avalue smaller than (or equal to) the gain Kd2 used in the formula (9)above.G3tgt(for acceleration)=Ka3·(K1·ΔD3+K2·Vsx)  (10)G3tgt(for deceleration)=Kd3·(K1·ΔD3+K2·Vsx)  (11)

Note that G3tgt is limited so as to be larger than an acceleration(G@TA=0) obtained when the throttle valve opening TA is equal to 0(G3tgt≤G@TA=0).

The target acceleration G3tgt for cut-in vehicle for decelerationcalculated based on the formula (11) above is limited so as not to beequal to or smaller than an acceleration (negative acceleration) G@TA=0realized/achieved when the throttle valve opening of the internalcombustion engine is “0 (or the minimum value within a range that thethrottle valve opening can become)” (namely, the throttle valve isfully-closed) while the brake device of the own vehicle VA is notoperated. That is, a process for limiting with a lower limit that is thethrottle valve fully closed acceleration G@TA=0 on the targetacceleration G3tgt for cut-in vehicle is performed. The throttle valvefully closed acceleration G@TA=0 may be said to be a minimumacceleration which the own vehicle VA can realize/achieve withoutoperating the brake device of the own vehicle VA.

More specifically, at step 460, the CPU calculates the targetacceleration G3tgt for cut-in vehicle according to either the aboveformula (10) or the above formula (11). The CPU sets the thus calculatedtarget acceleration G3tgt for cut-in vehicle at the throttle valve fullyclosed acceleration G@TA=0 if the thus calculated target accelerationG3tgt is smaller than the throttle valve fully closed accelerationG@TA=0. It should be noted that the CPU separately calculates thethrottle valve fully closed acceleration G@TA=0 based on the enginerotational speed NE and a gear position of an unillustrated transmissionof the own vehicle VA on the assumption that the CPU operates theinternal combustion engine under the fuel cut state when the throttlevalve opening is “0.” In this manner, the target acceleration G3tgt forcut-in vehicle is obtained based solely/only on the (coordinatetransformed) front-side looking radar information.

In contrast, when the CPU makes a “No” determination at either step 440or step 450, the CPU proceeds to step 445. The CPU sets the targetacceleration G2tgt for cut-in vehicle at the “imaginary accelerationG2infinite” which is larger than the maximum acceleration that the ownvehicle VA can realize, and sets the target acceleration G3tgt forcut-in vehicle at the “imaginary acceleration G3infinite” which islarger than the maximum acceleration that the own vehicle VA canrealize. Thereafter, the CPU proceeds to step 495 to end the presentroutine tentatively.

3. Mediation/Adjustment of Target Acceleration and Vehicle TravelControl

At an appropriate point in time, the CPU starts processing from step 700of a “routine for mediation of target acceleration and vehicle travelcontrol” shown in FIG. 7 , to execute processes of step 710 and step 720in this order, and proceeds to step 795 to end the present routinetentatively.

Step 710: The CPU selects one of the target acceleration G1tgt fortrailing travel, the target acceleration G2tgt for cut-in vehicle, andthe target acceleration G3tgt for cut-in vehicle, whichever is smallest,and sets the selected target acceleration as the “final targetacceleration (mediated/adjusted target acceleration) Gfin.” That is, theCPU mediates among three kinds of target accelerations. In other words,when the target acceleration G2tgt for cut-in vehicle, and the targetacceleration G3tgt for cut-in vehicle are considered to be a singletarget acceleration for cut-in vehicle, the CPU selects either thetarget acceleration for trailing travel or the target acceleration forcut-in vehicle, whichever is smaller, as the mediated targetacceleration Gfin.

Step 720: The CPU sends the mediated target acceleration Gfin to theengine ECU 30 and the brake ECU 40 in order to make the acceleration ofthe own vehicle VA become equal to the mediated target accelerationGfin. The engine ECU 30 and the brake ECU 40 control (drive) the engineactuators 32 and the brake actuators 42, respectively, based on themediated target acceleration Gfin. As a result, the actual accelerationof the own vehicle VA is made to become equal to the mediated targetacceleration Gfin. In this manner, the trailing inter-vehicle distancecontrol is performed.

As described above, the first device calculates the target accelerationG1tgt for trailing travel, the target acceleration G2tgt for cut-invehicle, and the target acceleration G3tgt for cut-in vehicle, and setsthe minimum (the smallest) target acceleration among them, as the “finaltarget acceleration (mediated/adjusted target acceleration) Gfin.”

Accordingly, when the target acceleration (one of G2tgt and G3tgt) forcut-in vehicle is selected as the mediated target acceleration Gfin in acase where the predicted cut-in vehicle is detected, the own vehicle VAdecelerates so as to increase the inter-vehicle distance between the ownvehicle VA and the objective-forward-vehicle. Thus, when the predictedcut-in vehicle actually cuts in, the inter-vehicle distance with respectto the cut-in vehicle (i.e., distance between the own vehicle VA and thepredicted cut-in vehicle that is now an actual cut-in vehicle) becomesappropriate in a short time. In addition, if theobjective-forward-vehicle starts to rapidly decelerate after a point intime at which the predicted cut-in vehicle is detected, it is likelythat the target acceleration G1tgt for trailing travel is selected asthe mediated target acceleration Gfin. Therefore, in this case, the ownvehicle VA decelerates so as to ensure/acquire an appropriateinter-vehicle distance with respect to the objective-forward-vehicle(i.e., appropriate inter-vehicle distance between the own vehicle VA andthe objective-forward-vehicle). As a result, the inter-vehicle distancebetween the own vehicle VA and the objective-forward-vehicle becomingexcessively short can be avoided, in a case where the predicted cut-invehicle does not actually cut in.

In addition, when the front looking radar device 21 and the front-sidelooking radar device (22L, 22R) detect the same (identical) targetobject, the first device integrates/merges the target object information(first target object information) that the front looking radar device 21obtains and the target object information (second target objectinformation) that the front-side looking radar device (22L, 22R) obtainsso as to obtain the integrated target object information. Thereafter,the first device determines the presence or absence of the predictedcut-in vehicle based on the integrated target object information, andfurther, calculates the target acceleration (G2tgt) for cut-in vehicleregarding (for) the predicted cut-in vehicle when the predicted cut-invehicle is determined to exist. The target acceleration (G2tgt) forcut-in vehicle may be set at a value obtained on the assumption that thebrake device is operated. In other words, the target acceleration(G2tgt) for cut-in vehicle is allowed to become a “negative accelerationwhose absolute value is large (i.e., large deceleration)”.

On the other hand, when the predicted cut-in vehicle is detected basedsolely/only on the “second target object information obtained by thefront-side looking radar device”, the first device obtains the targetacceleration (G3tgt) for cut-in vehicle while providing the limitationon the target acceleration (G3tgt) for cut-in vehicle in such a mannerthat the target acceleration (G3tgt) for cut-in vehicle does not becomesmaller than the “negative acceleration realized/achieved when thethrottle valve opening of the internal combustion engine of the ownvehicle VA is “0 (or, the throttle valve is fully-closed)” while thebrake device of the own vehicle VA is not operated”. Accordingly, whenthe cutting-in does not actually occur, the strong deceleration of theown vehicle VA due to the predicted cut-in vehicle does not occur. Thus,the driver avoids the odd feeling of rapid deceleration.

Second Embodiment

A vehicle travelling control device according to the second embodimentof the present disclosure (hereinafter, referred to as a “seconddevice”) will next be described. The second device is different from thefirst device only in the following points.

(1) The second device neither comprises the front-side looking radardevice 22L nor the front-side looking radar device 22R.

(2) The second device executes a routine shown in FIG. 8 in place of theroutines shown in FIGS. 3 and 4 , and executes a routine shown in FIG. 9in place of FIG. 7 .

Those different points will next be mainly described.

The CPU of the second device executes the “target accelerationcalculation routine” shown in FIG. 8 , every elapse of a predeterminedtime. It should be noted that the reference number given to the stepshown in FIG. 3 is given to a step shown in FIG. 8 whose process is thesame as the process of step shown in FIG. 3 . The detailed descriptionabout such a step will be omitted.

At an appropriate point in time, the CPU starts processing from step 800shown in FIG. 8 to execute the processes from step 310 to step 340 inthis order. Consequently, the target acceleration G1tgt for trailingtravel is calculated.

Subsequently, the CPU proceeds to step 810 to determine if there is apredicted cut-in vehicle. In this case, the CPU applies the lateraldistance Dfy(n) and the lateral relative speed Vfy(n) of each of “targetobjects other than the target object which is determined to be theobjective-forward-vehicle (a) at step 310, among the target objects (n)that the front looking radar device 21 detects” to the area map WS shownin FIG. 5 , so as to obtain the cut-in event probability P of each ofthe target objects. The CPU determines that there is a predicted cut-invehicle when there is a target object whose cut-in event probability Pis equal to or higher than the predetermined value (e.g., 60%),similarly to step 420. That is, the CPU specifies that target object asthe predicted cut-in vehicle.

When it is determined that there is the predicted cut-in vehicle, theCPU makes a “Yes” determination at step 810 to execute processes of step820 and step 830 described below in this order, and then, proceeds tostep 895 so as to end the present routine tentatively.

Step 820: The CPU calculates an inter-vehicle deviation (difference) ΔD4by subtracting the target inter-vehicle distance Dtgt from theinter-vehicle distance Dfx(b). The inter-vehicle distance Dfx(b) is theinter-vehicle distance Dfx(n) of the target object (b) which isdetermined to be the predicted cut-in vehicle at step 810. It should benoted that the target inter-vehicle distance Dtgt used at step 820 isreferred to as a “fourth set inter-vehicle distance”, as a matter ofconvenience. The fourth set inter-vehicle distance may be the same asthe first set inter-vehicle distance, or may be a value which becomescloser to the first set inter-vehicle distance from a value smaller thanthe first set inter-vehicle distance by a positive first value as an“elapsed time t from a point in time at which it was determined thatthere was the predicted cut-in vehicle” becomes longer. In this case,the target inter-vehicle time for calculating the fourth setinter-vehicle distance may be a time obtained by multiplying the “targetinter-vehicle time Ttgt used when the first set inter-vehicle distanceis calculated” by the “coefficient s(t)” which comes closer to andconverges on “1” from a value between “0” and “1” as the above mentionedtime t becomes longer.

Step 830: The CPU calculates the target acceleration G4tgt for cut-invehicle according to either one of a formula (12) and a formula (13)described below. The target acceleration G4tgt for cut-in vehicle isreferred to as a “fourth target acceleration”, as a matter ofconvenience.

In the formula (12) and the formula (13), Vfx(b) is the relative speedVfx(n) of the target object (b) which was determined to be the predictedcut-in vehicle at step 810, and “K1, and K2” are the same gains as the“K1, and K2” used in the formula (1) and the formula (2), respectively.The CPU uses the formula (12) below when a value (K1·ΔD4+K2·Vfx(b)) ispositive.

Ka4 is a positive gain (coefficient) for acceleration, and is set at avalue which is equal to or smaller than the gain Ka1 used in the aboveformula (1) (or than the gain Kat used at step 340 shown in FIG. 8 ).

The CPU uses the formula (13) below when the value (K1·ΔD4+K2·Vfx(b)) isnegative.

Kd4 is a positive gain (coefficient) for deceleration, and is set at avalue which is equal to or smaller than the gain Kd1 used in the aboveformula (2) (or than the gain Kd1 used at step 340 shown in FIG. 8 ).G4tgt(for acceleration)=Ka4·(K1·ΔD4+K2·Vfx(b))·  (12)G4tgt(for deceleration)=Kd4·(K1·ΔD4+K2·Vfx(b))  (13)

The target acceleration G4tgt for cut-in vehicle for decelerationcalculated based on the formula (13) above is calculated in such amanner that the target acceleration G4tgt is allowed to be anacceleration (negative acceleration) realized/achieved when the brakedevice of the own vehicle VA is operated, similarly to the targetacceleration G1tgt for trailing travel. In the above manner, the targetacceleration G4tgt for cut-in vehicle is calculated based solely/only onthe front looking radar obtained information.

In contrast, when the CPU determines that there is no predicted cut-invehicle upon the execution of step 810, the CPU makes a “No”determination at step 810 to proceed to step 840, at which the CPU setsthe target acceleration G4tgt for cut-in vehicle at the “imaginaryacceleration G4infinite” which is larger than the maximum accelerationthat the own vehicle VA can realize. Thereafter, the CPU proceeds tostep 895 to end the present routine tentatively.

Further, at an appropriate point in time, the CPU starts processing fromstep 900 a “routine for mediation of target acceleration and vehicletravel control” shown in FIG. 9 , to execute processes of step 910 andstep 920 in this order, and proceeds to step 995 to end the presentroutine tentatively.

Step 910: The CPU selects either one of the target acceleration G1tgtfor trailing travel and the target acceleration G4tgt for cut-invehicle, whichever is smaller, and sets the selected target accelerationas the “final target acceleration (mediated/adjusted targetacceleration) Gfin.” That is, the CPU mediates among two kinds of targetaccelerations.

Step 920: The CPU sends the mediated target acceleration Gfin to theengine ECU 30 and the brake ECU 40 in order to make the acceleration ofthe own vehicle VA become equal to the mediated target accelerationGfin. The engine ECU 30 and the brake ECU 40 control (drive) the engineactuators 32 and the brake actuators 42, respectively, based on themediated target acceleration Gfin. As a result, the actual accelerationof the own vehicle VA is made to become equal to the mediated targetacceleration Gfin. In this manner, the trailing inter-vehicle distancecontrol is performed.

As described above, the second device calculates the target accelerationG1tgt for trailing travel, and the target acceleration G4tgt for cut-invehicle, and sets the smaller target acceleration among them as the“final target acceleration (mediated/adjusted target acceleration)Gfin.”

Accordingly, similarly to the first device, when the target accelerationG4tgt for cut-in vehicle is selected as the mediated target accelerationGfin in a case where the predicted cut-in vehicle is detected, the ownvehicle VA decelerates so as to increase the inter-vehicle distancebetween the own vehicle VA and the objective-forward-vehicle. Thus, whenthe predicted cut-in vehicle actually cuts in, the inter-vehicledistance with respect to the cut-in vehicle (i.e., distance between theown vehicle VA and the predicted cut-in vehicle that is now an actualcut-in vehicle) becomes appropriate in a short time. In addition, if theobjective-forward-vehicle starts to rapidly decelerate after a point intime at which the predicted cut-in vehicle is detected, it is likelythat the target acceleration G1tgt for trailing travel is selected asthe mediated target acceleration Gfin. Therefore, in this case, the ownvehicle VA decelerates so as to ensure/acquire an appropriateinter-vehicle distance with respect to the objective-forward-vehicle(i.e., appropriate inter-vehicle distance between the own vehicle VA andthe objective-forward-vehicle). As a result, the inter-vehicle distancebetween the own vehicle VA and the objective-forward-vehicle becomingexcessively short can be avoided, in a case where the predicted cut-invehicle does not actually cut in.

The present disclosure is not limited to the embodiments describedabove, and various modifications may be adopted within the scope of thepresent disclosure. For example, as shown in FIGS. 1 and 2 , each of thefirst device and the second device may comprise a stereo camera 101which can communicate with the driving support ECU through the CAN 100.The stereo camera 101 is positioned at an upper portion of a frontwindow within a passenger room, and acquires a stereo image in astraight forward direction of the own vehicle VA. From the stereo image,the stereo camera 101 obtains the target object information, and lanemarkers (white lines). The stereo camera 101 can recognize the runninglane based on the lane markers, and the like. In this case, the firstdevice and the second device may obtain the objective-forward-vehicleand the predicted cut-in vehicle from the target object information thatthe front looking radar device 21 and the stereo camera 101 acquire.Further, the first device and the second device may estimate a course ofthe own vehicle VA based on the information concerning the running laneobtained from the stereo camera 101, and may modify the targetinformation which is obtained by the front looking radar device 21and/or the front-side looking radar device 22L, 22R in consideration ofthe estimated course, for example, in such a manner that the lateralposition of the target object become a target position in a directionorthogonal to the estimated course.

Further, the first device and the second device may be configured todetermine whether or not there is a predicted cut-in vehicle using a mapother than the map shown in FIG. 5 . For example, the first device andthe second device may be configured to determine whether or not there isa predicted cut-in vehicle in consideration of not only the lateralposition and the lateral relative speed of the vehicles other than theobjective-forward-vehicle but also the inter-vehicle distance of thevehicles.

What is claimed is:
 1. A vehicle travelling control device comprising:detecting means for detecting an objective-forward-vehicle traveling infront of an own vehicle and a vehicle which is predicted to cut inbetween said own vehicle and said objective-forward-vehicle; firstcalculation means for calculating a first target acceleration for theown vehicle to maintain an inter-vehicle distance between said ownvehicle and said objective-forward-vehicle at a first set inter-vehicledistance; second calculation means for calculating a second targetacceleration required for said own vehicle to maintain an inter-vehicledistance between said own vehicle and said predicted cut-in vehicle at asecond set inter-vehicle distance; mediation means for selecting, as amediated target acceleration, either said first target acceleration orsaid second target acceleration, whichever is smaller; and travelcontrol means for controlling a driving force and a brake force of saidown vehicle in such a manner that an actual acceleration of said ownvehicle becomes closer to said mediated target acceleration, wherein:said detecting means includes a front looking radar device having afront looking detection area, the front looking detection area having acenter axis extending in a straight forward direction of said ownvehicle, the front looking radar detects a target object to obtain firsttarget object information concerning said target object, and afront-side looking radar device having a front-side detection area, thefront-side detection area having a center axis extending in a diagonallyforward direction of said own vehicle, the front-side looking radardetects said target object to obtain second target object informationconcerning said target object; said vehicle travelling control devicefurther comprises predicted cut-in vehicle detecting means forintegrating said first target object information and said second targetobject information to obtain an integrated target object information,and detecting said predicted cut-in vehicle based on said integratedtarget object information, when said front looking radar device and saidfront-side looking radar device detect an identical target object, anddetecting said predicted cut-in vehicle based on said second targetobject information but not based on said first target objectinformation, when said front-side looking radar device detects saidtarget object, but said front looking radar device does not detect saidtarget object and said second calculation means calculates said secondfirst target acceleration in such a manner that said said second targetacceleration is allowed to be a negative acceleration achieved when abrake device of said own vehicle is operated, in a case where saidpredicted cut-in vehicle is detected based on said integrated targetobject information, and calculates said said second target accelerationwhile providing a limitation on said said second target acceleration insuch a manner that said said second target acceleration does not becomesmaller than a negative acceleration achieved when a throttle valveopening of an internal combustion engine serving as a driving force ofsaid own vehicle is set at a minimum value while said brake device ofsaid own vehicle is not operated, in a case where said predicted cut-invehicle is detected based on said second target object information butnot based on said first target object information.
 2. A vehicletravelling control device comprising: a radar system that detects anobjective-forward-vehicle traveling in front of an own vehicle and avehicle which is predicted to cut in between said own vehicle and saidobjective-forward-vehicle; an electronic control unit implemented by atleast one processor programmed and configured to calculate a firsttarget acceleration for the own vehicle to maintain an inter-vehicledistance between said own vehicle and said objective-forward-vehicle ata first set inter-vehicle distance, calculate a second targetacceleration required for said own vehicle to maintain an inter-vehicledistance between said own vehicle and said predicted cut-in vehicle at asecond set inter-vehicle distance, and select, as a mediated targetacceleration, either said first target acceleration or said secondtarget acceleration, whichever is smaller; an engine electronic controlunit; and a brake electronic control unit; wherein the engine electroniccontrol unit and the brake electronic control unit control a drivingforce and a brake force, respectively, of said own vehicle in such amanner that an actual acceleration of said own vehicle becomes closer tosaid mediated target acceleration, wherein said radar system includes afront looking radar device having a front looking detection area, thefront looking detection area having a center axis extending in astraight forward direction of said own vehicle, the front looking radardetects a target object to obtain first target object informationconcerning said target object, and a front-side looking radar devicehaving a front-side detection area, the front-side detection area havinga center axis extending in a diagonally forward direction of said ownvehicle, the front-side looking radar detects said target object toobtain second target object information concerning said target object,and wherein said electronic control unit is further configured tointegrate said first target object information and said second targetobject information to obtain an integrated target object information,and detect said predicted cut-in vehicle based on said integrated targetobject information, when said front looking radar device and saidfront-side looking radar device detect an identical target object,detect said predicted cut-in vehicle based on said second target objectinformation but not based on said first target object information, whensaid front-side looking radar device detects said target object, butsaid front looking radar device does not detect said target object,calculate said first second target acceleration in such a manner thatsaid first second target acceleration is allowed to be a negativeacceleration achieved when a brake device of said own vehicle isoperated, in a case where said predicted cut-in vehicle is detectedbased on said integrated target object information, and calculate saidfirst second target acceleration while providing a limitation on saidfirst second target acceleration in such a manner that said first secondtarget acceleration does not become smaller than a negative accelerationachieved when a throttle valve opening of an internal combustion engineserving as a driving force of said own vehicle is set at a minimum valuewhile said brake device of said own vehicle is not operated, in a casewhere said predicted cut-in vehicle is detected based on said secondtarget object information but not based on said first target objectinformation.